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Physics Department
The Cheerios Question
The Cheerios Question
A Physics students makes an observation one morning and then asks several friends, what happens when two cheerios are placed near each other in a bowl of milk (and why).
- A. The first student says - nothing particular happens. The Cheerios drift around at random (and become soggy). There are no net forces on the cheerios, so they just move with any random currents in the milk.
- B. The second student says that the Cheerios actually move apart, assuming the milk is at rest. They move apart because no matter how gently they are placed in the milk, tiny waves are generated by each Cheerio. These waves strike the other Cheerio causing it to move away from the first Cheerio.
- C. The third student says that the Cheerios actually move towards each other. This is caused by capillary action. The milk rises on the sides of the cheerios causing a horizontal component of force, which causes the cheerios to move towards each other.